During the packing of pourable, but somewhat bulky, products in foil tubular bags, the products have a tendency to bridge across the bag thereby clogging the bag. This can occur frequently as the bags are being filled. As a result, care has to be taken as the bags are being sealed to ensure that pieces of the bulk goods do not remain hanging in the region of the tubular bag being sealed. Bags are typically sealed at a seam between a pair of sealer jaws or tools. It is important to ensure that crumbly products and pieces do not remain hanging in the area of the sealed seam due to uncontrolled fall-in. Potato chips because of their low specific weight are a typical example of a troublesome product.
Even with very precise metering, due to the varying character of the product, pieces of the product filling the bag can float or remain hanging in the area of the seal at the moment that the sealing tools seal or close. If these pieces of product or bulk goods are sealed in the region of the seam, then the bag may remain open or seal in an unattractive fashion so as to be unsaleable.
In a typical bag producing device, the welding or sealing tools are mounted on pairs on rotating axles. The axles are positioned on both sides of the tubular foil and turn the sealing tools synchronously in such a way and at a rotational speed such that the opposing sealing tools meet each other after they pass the length of a bag. After meeting on opposing sides of the foil, a pair of tools travel straight together a short distance with the foil. The bag is subsequently sealed with a second pair of tools attached to the opposite side of the axles (i.e. the tools are offset 180 degrees).
Conventional seal tools typically have an associated closing bar that presses the tubular foil together. The seal tools also may include a stripper mounted on the turning axles, ensuring that the foil is pressed together and stripped before the sealing tools meet each other. The foil is thus prepared for the sealing process and at the same time, fall-in of the bulk goods into the area of the seal is prevented. The stripper removes the residue of the bulk goods on the inside of the tubular foil from the region of the seam.
European Patent Application 666215 A1 discloses a bag closing device in which the closing bars and the bar-shaped strippers are mounted on a support plate next to the support for the sealing tools and at a right angle to the foil passing through. The closing bars and the bar-shaped stripper swivel on their supports and are spring-loaded so that they can press the foil together as well as stripping the residue of the bulk goods from the area of the seal with a wiping motion.
To protect the welded tubular bags from the hot sealing tools, EPA 666215 A1 discloses wing-like shields attached to the bars and positioned between the just-sealed bag and the sealing tools. The closing bars serve as strippers, and are moved by the driveshafts. In order to ensure that the sealing tools press the tubular foil together and heat it for the time necessary for sealing, the tools are attached so that they are axially movable and are loaded with compression springs. The circular movement of the sealing tools is modified into a straight line during the sealing segment. One full rotation of the axles that support the sealing tools produces two sealing processes.
The disclosed device has several disadvantages. The attachment and bearing of the necessary components makes installation difficult, requires space, and makes the device sluggish in its movements, thereby also reducing the clock rate of the packing device. Furthermore, because the rotating movement cycles and movement axes can only be positioned opposite to one another in a limited way, the effective zones of the closing bars and the strippers are restricted to a limited area.
The sealing device disclosed in U.S. Pat. No. 4,663,917 operates in a similar manner. German Patent Application No. DE 400 50 078 discloses a sealing device in which the closing bars are attached to the sealing heads directly using springs. The foil on both sides of the sealing tools or jaws is pressed together by the spring-loaded closing bars. A stripping motion is not provided in this design.
The device disclosed in German Patent Application No. DE 24 01 800 does use a stripper, but the stripper only functions as the closing bars described above. A direct connection and movement of this component with the sealing tool in the sense of a stripping movement is not given.
Thus, there remains a need for a bag producing device that includes closing bars and strippers positioned directly on the sealing tool or the tool mount, that provides for movement of these elements so that a secure operating cycle is produced at a high clock frequency.
According to the present invention a device for the production of tubular bags filled with bulk goods from a continuous foil tube moving in a run direction is provided. The device may include a pair of sealing tools that seal the foil tube in bag-length intervals; a pair of closing bars provided for the tools and directly clamped to the sealing tools, each closing bar biased toward the other closing bar for pressing the foil tube before the sealing tools are closed; and a stripper, which can touch the foil tube, through which the residue of the bulk goods can be removed from the area of the seal by a wiping motion effective in the run direction. The closing bars may be connected to the stripper so that through a closing movement of the closing bars, the stripper is pulled along in the run direction while touching the foil before the sealing tools close.
Preferably, the closing bars are connected to support bars which pass through clamps positioned on the sealing tools and wherein each support bar is loaded against the closing movement of the sealing tools by a return spring. The stripper may be connected to the sealing tools so that the stripper is pulled by the movement of the support bars against the force of the springs in a swinging movement while touching the foil, out of the area where the sealing tools touch the foil. The swinging movement of the stripper typically covers a distance at least three times greater than the distance moved by the support bars. The movement of the support bar is mechanically transmitted to the stripper by a positioner attached to the sealing tool. The positioner may include a tracer pin and the support bar may have a slanted surface positioned to contact an end of the tracer pin.
In an alternative embodiment, the present invention may include a device for the production of tubular bags filled with bulk goods from a continuous foil tube moving through the device. The device may include a pair of moveable sealing tools positioned on opposite sides of the foil tube, the sealing tools configured to come together to seal the tube. Each sealing tube may include a closing bar biased toward the closing bar on the opposing sealing tool and adapted to move with the sealing tool to contact the tube; a sealing jaw positioned opposite the sealing jaw on the opposing sealing tool so that when the sealing tools come together the sealing jaws contact the tube to thereby seal the tube; and a stripper located downstream from the closing bar in the direction of movement of the foil tube and being configured to move along the tube in the direction the tube is moving to strip the bulk goods away from the area of the tube to be sealed at the same time that the sealing jaw is moving toward the tube.
The closing bars may move in a direction generally perpendicular to the direction of movement of the tube and are biased toward each other by a spring. Each sealing tool may further comprise a support bar connected to the closing bar and aligned in the direction of movement of the closing bar. The support bar may be configured to move in a direction generally perpendicular to the movement of the tube against the bias on the closing tube.
The stripper may include a stripper bar. The stripper bar may be connected to the closing bar so that movement of the closing bar causes movement of the stripper bar along the tube in the direction the tube is moving. A tracer pin may be provided so that when the support bar moves the motion of the support bar is transferred to the stripper through the pin. The end of the support bar adjacent the pin may include a tapered surface so that as the end of the support bar moves away from the tube the tapered surface slides along an end of the pin to thereby force the pin to move in a longitudinal direction. The pin is generally positioned between the support bar and the stripper so that when the pin is forced to move in the longitudinal direction by the support bar the other end of the pin contacts the stripper to cause the stripper to move along the surface of the foil away from the sealing jaws and the area of the foil to be sealed.
The stripper bar may be connected to a mechanical linkage pivotally mounted to the sealing tool. The tracer pin may be positioned between the support bar and the mechanical linkage so that linear movement of the support bar is translated to swinging movement of the mechanical linkage.
It is to be understood that both the foregoing general description and following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.